Make bits/wchar.h correct for all architectures (bug 15036).

1 files changed, 26 insertions, 2 deletions

diff --git a/bits/wchar.h b/bits/wchar.h
index eb07151152..ef93d0e784 100644
--- a/bits/wchar.h
+++ b/bits/wchar.h
@@ -19,7 +19,31 @@
 #ifndef _BITS_WCHAR_H
 #define _BITS_WCHAR_H	1
 
-#define __WCHAR_MIN	(-2147483647 - 1)
-#define __WCHAR_MAX	(2147483647)
+/* The fallback definitions, for when __WCHAR_MAX__ or __WCHAR_MIN__
+   are not defined, give the right value and type as long as both int
+   and wchar_t are 32-bit types.  Adding L'\0' to a constant value
+   ensures that the type is correct; it is necessary to use (L'\0' +
+   0) rather than just L'\0' so that the type in C++ is the promoted
+   version of wchar_t rather than the distinct wchar_t type itself.
+   Because wchar_t in preprocessor #if expressions is treated as
+   intmax_t or uintmax_t, the expression (L'\0' - 1) would have the
+   wrong value for WCHAR_MAX in such expressions and so cannot be used
+   to define __WCHAR_MAX in the unsigned case.  */
+
+#ifdef __WCHAR_MAX__
+# define __WCHAR_MAX	__WCHAR_MAX__
+#elif L'\0' - 1 > 0
+# define __WCHAR_MAX	(0xffffffffu + L'\0')
+#else
+# define __WCHAR_MAX	(0x7fffffff + L'\0')
+#endif
+
+#ifdef __WCHAR_MIN__
+# define __WCHAR_MIN	__WCHAR_MIN__
+#elif L'\0' - 1 > 0
+# define __WCHAR_MIN	(L'\0' + 0)
+#else
+# define __WCHAR_MIN	(-__WCHAR_MAX - 1)
+#endif
 
 #endif	/* bits/wchar.h */